One SQL master table record corresponds to multiple record statements in the attached table

One SQL master table record corresponds to multiple record statements in the attached table

In this case, we will use

Union statement

SQL union syntax

Select column_name (s) from table_name1
Union
Select column_name (s) from table_name2

Join left statement

Left join keyword syntax

Select column_name (s)
From table_name1
Left join table_name2
On table_name1.column_name = table_name2.column_name

Where subquery

Select * from a B where a. id = B. id

Here is an example.

Select xxxx from main table inner join appendix on main table. xxxx = appendix. xxxx where xxxx

Instance description.

Employees_china:
E_id e_name
01 zhang, hua
02 wang, wei
03 carter, thomas
04 yang, ming

Employees_usa:
E_id e_name
01 adams, john
02 bush, george
03 carter, thomas
04 gates, bill

List all different employee names in China and the United States:

Select e_name from employees_china
Union
Select e_name from employees_usa
Result
E_name
Zhang, hua
Wang, wei
Carter, thomas
Yang, ming
Adams, john
Bush, george
Gates, bill